Different codes have different uses, and a good code is one that can be decoded fairly quickly, but only if you have the key.
There are different types of codes: ones with numbers, letters, symbols, or a mix of any of these! This is simply a handy database of different common codes that anyone can learn.
Here is the list of codes that you can use to help you learn!
If you've learned some codes and want to test your skills, you can go here to practice some of them!